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. 2014 Mar 4:5:69.
doi: 10.3389/fmicb.2014.00069. eCollection 2014.

Metabolic versatility in Haemophilus influenzae: a metabolomic and genomic analysis

Dk Seti Maimonah Pg Othman  1 , Horst Schirra  2 , Alastair G McEwan  1 , Ulrike Kappler  1
Affiliations

Metabolic versatility in Haemophilus influenzae: a metabolomic and genomic analysis

Dk Seti Maimonah Pg Othman et al. Front Microbiol. .

Abstract

Haemophilus influenzae is a host adapted human pathogen known to contribute to a variety of acute and chronic diseases of the upper and lower respiratory tract as well as the middle ear. At the sites of infection as well as during growth as a commensal the environmental conditions encountered by H. influenzae will vary significantly, especially in terms of oxygen availability, however, the mechanisms by which the bacteria can adapt their metabolism to cope with such changes have not been studied in detail. Using targeted metabolomics the spectrum of metabolites produced during growth of H. influenzae on glucose in RPMI-based medium was found to change from acetate as the main product during aerobic growth to formate as the major product during anaerobic growth. This change in end-product is likely caused by a switch in the major route of pyruvate degradation. Neither lactate nor succinate or fumarate were major products of H. influenzae growth under any condition studied. Gene expression studies and enzyme activity data revealed that despite an identical genetic makeup and very similar metabolite production profiles, H. influenzae strain Rd appeared to favor glucose degradation via the pentose phosphate pathway, while strain 2019, a clinical isolate, showed higher expression of enzymes involved in glycolysis. Components of the respiratory chain were most highly expressed during microaerophilic and anaerobic growth in both strains, but again clear differences existed in the expression of genes associated e.g., with NADH oxidation, nitrate and nitrite reduction in the two strains studied. Together our results indicate that H. influenzae uses a specialized type of metabolism that could be termed "respiration assisted fermentation" where the respiratory chain likely serves to alleviate redox imbalances caused by incomplete glucose oxidation, and at the same time provides a means of converting a variety of compounds including nitrite and nitrate that arise as part of the host defence mechanisms.

Keywords: Haemophilus influenzae; carbon metabolism; enzymes; gene expression; proton NMR.

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Figures

Figure 1
Figure 1
Schematic representation of H. influenzae pathways for central carbon metabolism (A) and the elements of the respiratory chain (B). Abbreviations: pyruvate dehydrogenase complex, aceF; Pyruvate formate lyase, pflA; Acetate kinase, ackA; NAD+-dependent D-lactate dehydrogenase, ldhA; Formate dehydrogenase, fdxG; NADH dehydrogenase, ndh; NADH dehydrogenase, nqr; L - Lactate dehydrogenase, lldD; D-Lactate dehydrogenase, dld; Cytochrome bd oxidase, cydA, cydB; DMSO reductase, dmsA; Nitrate reductase, napA; TMAO reductase, torZ; Nitrite reductase, nrfA; Fumarate reductase, frdA; malate dehydrogenase, mdh; PEP carboxylase, ppc; PEP carboxykinase, pckA; 2-oxoglutarate dehydrogenase, sucAB; Succinyl-CoA synthetase, sucCD; fumarate hydratase, fumC.
Figure 2
Figure 2
Changes in metabolite concentrations in cultures of H. influenzae RD and 2019 grown under aerobic (closed circles), microaerophilic (open circles), and anaerobic (closed triangles) conditions. The data shown is for two growth substrates, pyruvate and glucose (rows 1 and 2) and two key metabolites produced during growth, acetate, and formate (rows 3 and 4).
Figure 3
Figure 3
Expression of genes involved in central carbon metabolism and respiration in H. influenzae RDKW20 for cultures grown under aerobic (A) microaerophilic (B) and anaerobic (C) conditions. Black bars: Genes relevant for glucose catabolism, White bars: Genes relevant for pyruvate conversions, gray bars: genes relevant for respiratory metabolism. Abbreviations of gene names: Glucose 6-phosphate dehydrogenase, zwf; pyruvate dehydrogenase complex, aceF; Pyruvate formate lyase, pflA; Acetate kinase, ackA; NAD+-dependent D-lactate dehydrogenase, ldhA; Formate dehydrogenase, fdxG; NADH dehydrogenase, ndh; NADH dehydrogenase, nqrB; L-Lactate dehydrogenase, lldD; D-Lactate dehydrogenase, dld; Cytochrome bd oxidase, cydA, cydB; DMSO reductase, dmsA; Nitrate reductase, napA; TMAO reductase, torZ; Nitrite reductase, nrfA; Fumarate reductase, frdA.
Figure 4
Figure 4
Enzyme activities of DMSO reductase (A) and Formate dehydrogenase (B) in H. influenzae RD under aerobic, microaerophilic, and anaerobic growth conditions. Assays were conducted with at least three repetitions, the experimental error is reported as standard error of the mean.
Figure 5
Figure 5
Expression of genes involved in central carbon metabolism and respiration in H. influenzae 2019 for cultures grown under aerobic (A) microaerophilic (B) and anaerobic (C) conditions. Black bars: Genes relevant for glucose catabolism, White bars: Genes relevant for pyruvate conversions, gray bars: genes relevant for respiratory metabolism. Abbreviations of gene names: Glucose 6-phosphate dehydrogenase, zwf; pyruvate dehydrogenase complex, aceF; Pyruvate formate lyase, pflA; Acetate kinase, ackA; NAD+-dependent D-lactate dehydrogenase, ldhA; Formate dehydrogenase, fdxG; NADH dehydrogenase, ndh; NADH dehydrogenase, nqrB; L-Lactate dehydrogenase, lldD; D-Lactate dehydrogenase, dld; Cytochrome bd oxidase, cydA, cydB; DMSO reductase, dmsA; Nitrate reductase, napA; TMAO reductase, torZ; Nitrite reductase, nrfA; Fumarate reductase‡, frdA.
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References

    1. Alexander H. E. (1965). “The haemophilus group,” in Bacterial and Mycotic Infections of Man, eds Dabos R. J., Hirsch J. G. (London: Pitman Medical Publishing Co. Ltd; ).
    1. Alteri C. J., Lindner J. R., Reiss D. J., Smith S. N., Mobley H. L. T. (2011). The broadly conserved regulator PhoP links pathogen virulence and membrane potential in Escherichia coli. Mol. Microbiol. 82, 145–163 10.1111/j.1365-2958.2011.07804.x - DOI - PMC - PubMed
    1. Alteri C. J., Mobley H. L. T. (2012). Escherichia coli physiology and metabolism dictates adaptation to diverse host microenvironments. Curr. Opin. Microbiol. 15, 3–9 10.1016/j.mib.2011.12.004 - DOI - PMC - PubMed
    1. Ausubel F. M., Brent R., Kingston R. E., Moore D. D., Seidman J. G., Smith J. A., et al. (2005). “Current protocols in molecular biology,” in Current Protocols in Molecular Biology, ed Janssen K. (Hoboken, NJ: John Wiley & Sons Inc; ).
    1. Berkovitch M., Bulkowstein M., Zhovtis D., Greenberg R., Nitzan Y., Barzilay B., et al. (2002). Colonization rate of bacteria in the throat of healthy infants. Int. J. Pediatr. Otorhinolaryngol. 63, 19–24 10.1016/S0165-5876(01)00635-8 - DOI - PubMed

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